Acquisitions - Security California Bancorp - Narrative (Details) $ / shares in Units, $ in Thousands	Jan. 31, 2016 USD ($) bank shares	Mar. 31, 2016 USD ($)	Jan. 29, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)
Business Acquisition [Line Items]
Assets		$ 3,563,085		$ 2,790,646	$ 2,753,000
Loans		2,857,775		2,262,683	2,130,853
Deposits		2,906,264		2,195,123	2,043,166
Closing stock price of common stock ($ per share) | $ / shares			$ 20.53
Goodwill		$ 102,085		$ 50,832	$ 51,010
Security California Bancorp
Business Acquisition [Line Items]
Assets	$ 714,000
Loans	456,000
Deposits	$ 637,000
Equity issued (shares)	0.9629
Consideration paid	$ 120,174
Cash consideration	$ 788
Number Of branches | bank	6
Goodwill	$ 51,252
Common Stock | Security California Bancorp
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration | shares	5,815,051
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			$ 119,400